interior lights

does anyone have any idea about my interior lights they quit working the other day checked all fuses with multimeter all are good when i honk the horn it has quit working too but when you honk horn no sound but interior lights light up and there is a loud buzz coming from under dash lol and when the doors are open the cigarette lighter quits working shut doors and it comes back on any help on this would be greatly appreciated im thinking its a relay gone bad but i want to be sure before spending money on relays and it being something else by the way its an 85 suburban 5.7 2wd c10

I'm thinking it's a bad/dirty/broken ground somewhere. There are many ground points, under dash, at the doors, frame grounds, body grounds. I don't know where to suggest you start looking, but under the dash is as good and anywhere to start.